Around 50,000 people in the U.S. are diagnosed with Parkinson’s disease (PD) every year. The American Institute of Neurology estimates there are around one million people who are affected with PD, with 60 years as the average age of onset. Falls and fall-related injuries are a huge problem for people with Parkinson’s. Up to 70 percent of advanced PD patients fall at least once a year and two-thirds suffer from recurring falls. The fall rates are twice as high in adults of a comparable age. Improving balance in patients with Parkinson’s would be a huge health advantage.
Sunil Agrawal, professor of mechanical engineering and rehabilitation and regenerative medicine at Columbia Engineering, and Dario Martelli, a post-doctoral researcher in his group, have been working together with Movement Disorders faculty from the Department of Neurology at Columbia University Medical Center, Stanly Phan, a lead expert in Parkinson’s, Un Jung Kang, division director, and Lan Luo, Movement Disorder Fellow.
The team looked at whether Parkinson’s disease affects patients’ balance and diminishes their ability to react and adapt to walking with distresses. The researchers found that the ability to adapt to multiple perturbations, or to modify responses to changing amplitudes or directions, was not affected by PD. The subjects with Parkinson’s and the healthy subjects controlled their reactive strategies in similar ways. Both groups improved their unperturbed walking after a single training session with repeated waist pull perturbations.
Agrawal’s team used a robotic system, Tethered Pelvic Assist Device (TPAD) in their study. The TPAD is a wearable, lightweight cable-driven robot that can be programmed to provide forces on the pelvis in the desired direction as the subject walks on a treadmill. In an earlier study, Agrawal successfully used the TPAD in order to improve posture and walking in children with cerebral palsy.
"Most falls in PD are reported during walking, and gait disorders are one of the hallmarks of PD, but previous studies on PD subjects have focused on responses to balance perturbations only while standing," said Agrawal, also a member of the Data Science Institute. "Our TPAD has enabled us for the first time to study how subjects respond to repeated pelvic perturbations during walking, and to characterize reactive and adaptive responses to these perturbations among the young, old and PD patients."
Nine PD patients and nine age-matched control subjects participated in the study. The researchers evaluated the margin to stability and base of support while the study participants walked on the treadmill without cables. The participants were then hooked up to the TPAD’s cables and given waist-pull diagonal perturbations for short periods of time, in order to assess their reactions.
Each group was then trained with 72 randomly applied pelvic force perturbations that varied in direction (forward/backward/sideways), intensity (low/medium/high) and the specific foot (right/left) in contact with the ground. After the training period, they walked freely without the cables and underwent the same diagonal perturbations they had been given before training. The post-sessions were conducted to assess the effects of training on their balance and stability.
The researchers found that the Parkinson’s patients had a reduced stability in the forward direction before and after training, compared to the healthy subjects and an inability to produce proactive anticipatory adjustments. When all of the subjects had complete the training session, both groups were able to improve their response to the perturbations, but also produce short-term aftereffects of increased gait stability.
"Our data showed that one single session of perturbation-based balance training produced acute effects that ameliorated gait instability in PD patients," said Martelli, the paper's first author. "This result is encouraging for designing new therapeutic interventions that remediate falls risk."
While current training methods, like conventional exercises at the gym, target volitional movements of the body, they don’t address the specific neuromuscular skills that are required for fall prevention.
"This novel TPAD provides an insight into the specific mechanisms underlying the propensity of PD patients to fall and the ability to address these specific deficits to train them to avoid falls. The potential impact of such training to prevent accompanying morbidity from the falls and to improve their quality of life is great," Kang said.
"We believe that new training programs, in coordination with new robotic devices such as Columbia Engineering's TPAD, should be developed where unexpected force perturbations are given to the human subjects in a controlled way that allows the human brain to develop control strategies to respond to these perturbations, maintain balance and avoid falls," Fahn added.
The researchers are currently planning future studies to examine if a multi-session training program will demonstrate more lasting effects on walking balance, improve function and reduce the number of falls in long-term assessments.
The paper on this research was published in Scientific Reports.